AEM CAI Tubing size plss ..

Would like to know what is the exact inside diameter of the CAI sytem tubing of AEM (as featured in the diy section) .. trying to do a copy of it using aluminium tubing coated in ceramic paint.
Would a 55mm do ? for a jdm d15b ? or is it slightly too small .. i have a3 inch short ram but i think a smaller tubing would be better .. any info on this ?

for a d15, 3 inches is a good start, the d series can only suck in so much, but make sure that for what air you have going into the motor, that you have adequete airflow out of the motor (i.e. header, exuast), otherwise that bigger intake isn't going to be as affective as you hope it will be. good luck